Seat Belts... wear them! Watch the vid0 at the end of this post .

The Human Collision
Imagine running as fast as you can - into a wall. You'd expect to get pretty banged up. Do you think you could stop yourself if the wall suddenly loomed up when you were two feet away from it? This is exactly the situation you face when the front of your car hits something at only 15 miles an hour. The car stops in the first tenth of a second, but you keep on at the same rate you were going in the car until something stops you - the steering wheel, dashboard or windshield - if you're not wearing your safety belt.. Bad enough at 15 miles an hour, but a 30 miles you hit "the wall" four times as hard as you would at 15. Or to put it another way, with the same impact you'd feel as if you fell three stories.
Seat Belt Safety: 5-Way Protection
“Seat belts prevent occupants of the vehicle from serious injury in five ways,” says Angela Osterhuber, director of the Pennsylvania Traffic Injury Prevention Project in Media, Pa. A seat belt:

* Keeps the occupants of the vehicle inside. “It’s clearly a myth that people are better off being thrown clear from the crash,” Osterhuber says. “People thrown from a vehicle are four times more likely to be killed than those who remain inside.”
* Restrains the strongest parts of the body. “Restraints are designed to contact your body at its strongest parts. For an older child and adult, these parts are the hips and shoulders, which is where the seat belt should be strapped,” Osterhuber says.
* Spreads out any force from the collision. “Lap-and-shoulder belts spread the force of the crash over a wide area of the body. By putting less stress on any one area, they can help you avoid serious injury,” Osterhuber says. A shoulder strap also helps keep your head and upper body away from the dashboard, steering wheel, and other hard interior parts of the automobile should you stop suddenly or be hit by another vehicle.
* Helps the body to slow down. “What is it that causes injury? A quick change in speed,” Osterhuber says. “Seat belts help extend the time it takes for you to slow down in a crash.”
* Protects your brain and spinal cord. A seat belt is designed to protect these two critical areas. “Head injuries may be hard to see immediately, but they can be deadly,” Osterhuber says. Likewise, spinal cord injuries can have serious consequences. by Beth W. Orenstein. http://www.everydayhealth.com/healthy-living/wearing-your-seat-belt.aspx